Molding of a shock resistant transparent polymer sphere

ABSTRACT

An example of the shock resistant transparent polymer sphere is a billiard or pool ball. The molding apparatus includes lower and upper mold halves defining juxtaposed concave hemispherical surfaces to define a spherical mold cavity with a top fill opening on the upper mold half. Interlocking of the mold halves together is accomplished by tongue and window structures circumferentially spaced about the meeting points of the two halves at 120°. A holder in the form of an annular ring is provided for supporting a central disc provided with a symbol on each of its opposite faces. The design is such that the ring when positioned in the spherical cavity defined by the mold halves supports the disc with its center coincident with the center of the spherical cavity. The molded sphere is made by a single pouring operation of resin through the fill opening, the disc and ring being encapsulated within the sphere. The composition of the resulting product is such that a bonding takes place between the disc, ring and resin material for the sphere resulting in a final sphere in which shock is absorbed by the disc, supporting ring, ink utilized in forming the symbol on the opposite faces of the disc as well as the resin as though the entire sphere were homogeneous throughout.

This is a division of application Ser. No. 857,297 filed Dec. 5, 1977.

This invention relates to a molding apparatus, method and productcomposition for providing shock resistant transparent polymer spheresuseful, by way of example, as pool or billiard balls.

BACKGROUND OF THE INVENTION

Spherical objects utilized in games such as pool or billiards arenormally homogeneous throughout so that the shock of impact will bethoroughly, uniformly absorbed throughout the entire mass of the ball.In the case of a pool ball, a number designation identifying the ball isprovided on one or more surface portions of the ball, the ballsthemselves normally being opaque.

A very attractive type of pool ball would result if a transparentmaterial could be used in molding the ball. In such instances, however,provision of a designating numeral on the surface would interrupt thetransparent feature of the ball and it would be preferable if thedesignating numeral could someway be incorporated or encapsulated withinthe ball.

It is already known to provide a transparent bowling ball encapsulatinggeometric designs to enhance and provide a novel appearance for thebowling ball. In this respect, reference is had to U.S. Pat. No.3,207,514 to Vickery claiming such a structure. However, so far as weare aware, there has never heretofore been produced a transparent poolor billiard ball incorporating an appropriate number designation untilthe invention of Robert James Chavarria and Clark Berg Foster asdisclosed and claimed in copending patent application Ser. No. 728,498filed Sept. 28, 1976, now U.S. Pat. No. 4,116,439, and entitled POOLBALL.

The foregoing application discloses molding apparatus, a molding method,and a completed transparent pool ball product. Nevertheless, effectivebonding between the incorporated numeral carrier in the sphere and thesphere material itself as well as the ink or other means for providing anumeral or symbol has not always been assured. As a consequence,shattering of the ball along cleavage planes where improper bondingoccurs can result. Moreover, surface deterioration and imperfections aredifficult to avoid.

BRIEF DESCRIPTION OF THE PRESENT INVENTION

Bearing the foregoing in mind, the present invention contemplates animproved molding apparatus, method and product composition for providingshock resistant transparent polymer spheres such as pool balls and inits preferred embodiment is specifically concerned with the formation oftransparent pool balls encapsulating an appropriate opaque disc having anumeral designation on its opposite faces to identify the ball.

Essentially, this improved invention, as a consequence of the moldingapparatus, method and composition employed provides a vastly improvedpool ball wherein impact shocks are absorbed by the resin of the ball aswell as the encapsulated materials in the ball all the same as though ahomogeneous ball were provided. Further, the molding apparatus andmethod of molding and the compositions employed in accord with thisinvention assure bonding of the encapsulated portions with the resin ofthe sphere in such a manner as to minimize the risk of any cleavageplanes which would result in shattering of the ball upon impact.

BRIEF DESCRIPTION OF THE DRAWINGS

A complete understanding of this invention as well as many otherfeatures and advantages resulting therefrom will be had by now referringto the accompanying drawings in which:

FIG. 1 is an exploded perspective view with portions cut away of amolding apparatus in accord with this invention;

FIG. 2 is a fragmentary cross section of a portion of the structure ofFIG. 1 when in assembled relationship;

FIG. 3 is another fragmentary cross section of the assembled structureof FIG. 1 looking in the direction of the arrow 3;

FIG. 4 is a side elevational view of a disc-ring assembly shown in FIG.1 for encapsulation; and,

FIG. 5 is a perspective view of a finished pool ball product formed inaccord with the method and apparatus of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, the molding apparatus itself includes a lower moldhalf 10 defining an upwardly facing concave hemispherical surface 11.The upper exterior marginal wall of the surface 11 is cylindrical asshown at 12 for a given vertical distance downwardly, this surfacethence extending laterally outwardly to define a flat annular upwardlyfacing shoulder 13.

An upper mold half 14 defines a downwardly facing concave hemisphericalsurface 15. The lower interior wall of this surface has an increaseddiameter portion at the lower edge of said downwardly facing concavehemispherical surface defining an interior cylindrical wall 16 extendingdownwardly beyond the edge the same given vertical distance as theexterior wall 12 of the lower mold half. The interior cylindrical wall16 thence extends laterally to define a flat annular downwardly facingshoulder 17 for seating on the upwardly facing shoulder 13 when theexternal marginal wall 12 is received in the internal cylindrical wall16 so that the upwardly facing and downwardly facing concavehemispherical surfaces are juxtaposed to define a spherical cavity.

Referring to the central portion of FIG. 1, there is shown a disc 18provided with a symbol 19 on each of its opposite faces. In theembodiment disclosed, this symbol constitutes the numeral 12 and servesto identify a pool ball within which the disc will ultimately beencapsulated.

The disc 18 is diametrically held in the spherical cavity of the mold sothat its center coincides with the center of the spherical cavity.Towards this end, there is provided a holder for the disc in the form ofan annular ring 20 having a plurality of lugs 21, 22 and 23 extendingradially inwardly equal distances to engage the periphery of the disc 18at equal circumferentially spaced points. The disc is thus held insidethe ring in substantially coplanar relationship.

The exterior of the ring includes at least two locating pins 24 and 25extending radially outwardly, and a centering projection 26 shown at thebottom of the ring 20. The pins and centering projection are spaced at120°, the bottom-most point on the upwardly facing hemispherical surfacehaving a hole 27 receiving the end portion of the centering projection26'.

The diameter of the holder as measured out to the tips of the pins andthe start of the end portion of the centering projection 26 is indicatedat D and is substantially the same as the diameter of the hemisphericalsurface also designated by the same letter D in FIG. 1.

With the foregoing arrangement, the disc 18 will necessarily be held ina diametric position within the spherical cavity defined by thejuxtaposed hemispherical surfaces 11 and 15 of the lower and upper moldhalves respectively, the centering projection 26 having its end portion26' received in the central bottom opening 27 of the lower mold half 11and the locating pins 24 and 25 touching lightly the downwardly facinghemispherical surface 15.

The top center of the upper mold half 14 includes a fill opening 28 forintroducing molding material. The exterior walls of the lower and uppermold halves further may be provided with gripping lands or ribs asindicated at 29 and 30 respectively. In this respect, the flat upwardlyfacing annular shoulder 13 and the flat downwardly facing annularshoulder 17 include cooperating fastening means for holding the moldhalves together, this fastening means being responsive to relativetwisting of one mold half with respect to the other. The provision ofthe lands or ribs on the exterior of the mold halves facilitates thismanual twisting to lock the halves together or to release the halves.

The foregoing mentioned cooperating fastening means in the specificembodiment shown includes three windows on the flat upwardly facingannular shoulder 13 spaced 120° from each other. Only one of thesewindows is visible as indicated at 31 in FIG. 1. The flat downwardlyfacing annular shoulder 17 in turn is provided with three flexibletongues extending at an acute angle to the shoulder receivable in thewindows, when the upper mold is rotated in the direction of extension ofthe tongues relative to the lower mold half. Only one of these tonguesis visible at 32 in FIG. 3.

The foregoing locking feature can better be understood by now referringto FIGS. 2 and 3. FIG. 2 illustrates the seating of the lower and upperannular shoulders 13 and 17 and it will be understood that whenpositioning the upper mold half on the lower mold half, the tongues 32are indexed to enter the windows 31.

FIG. 3 illustrates the relative positions of the tongue and windowsafter the same have been received through the window and the upper moldhalf twisted relative to the lower mold half in a clockwise direction asviewed from the top. It will be evident that the tongue 32 has beenlocked under an edge of the window 31. In this respect, curvedcooperating camming surfaces are provided as indicated at 33 for holdingthe tongues in their final positions within the windows. Thus, the edgeportion of the window 31 under which the tongue 32 slides is providedwith an enlarged rounded cross section as shown in FIG. 3, the tongue 32itself having a depressed or curved portion for receiving this roundedportion when the tongue is wholly disposed beneath the edge of thewindow thus providing an indexing or locking of the mold halvestogether. When the upper mold half is to be removed from the lower moldhalf, a twist in the opposite direction will result in a camming down ofthe tongue 32 by the rounded portion 33 so that release of the tonguethrough the window can take place.

In the description of the disc 18 and holding ring 20 in FIG. 1, it willbe recalled that the disc 18 was described as being substantiallycoplanar with the ring 20. To effect this coplanar relationship, it isnecessary that the medial plane of the disc 18 coincide with the medialplane of the ring 20. The ring 20 itself has a thickness which is lessthan the thickness of the disc 18 and thus for proper centering, theopposite faces or surfaces of the disc 18 must extend equal distancesbeyond the opposite faces of the annular ring 20.

To assure the above described proper positioning of the disc relative tothe ring, reference is had to FIG. 4 wherein it will be noted that thering includes axially extending nubs from its opposite flat surfaces,one such nub being indicated at 34 in FIG. 4. These nubs terminate inthe plane of the opposite surfaces of the disc when the disc is centeredin the ring. Accordingly, proper axial centering of the disc in the ringcan be effected by engaging a flat surface indicated at 35 in FIG. 4with one surface of the disc and the corresponding ends of the nubs 34.

The method of manufacturing a shock resistant transparent polymer spheresuch as a pool ball with a disc having a symbol inked on each of itsopposite faces diametrically incorporated in the sphere with the centerof gravity of the disc coincident with the center of gravity of thesphere utilizing the molding apparatus of FIGS. 1-4 will now bedescribed.

First, a mold is provided defining a spherical cavity with a single fillopening at its top. This spherical cavity may be provided by the moldhalves shown in FIG. 1.

A given transparent polyester resin in uncured liquid form is thenprovided preparatory to pouring into the mold. One type of polyesterresin is identified as "Clear Cast" manufactured by Fiberlay, Inc. ofSeattle, Wash. This resin is preferably mixed with an appropriatecatalyst to harden the resin after pouring. Such a catalyst isidentified by "P-102" manufactured by the same company as "Clear Cast."Additionally, a "surface seal" may be added to the mixture to avoid atacky surface upon hardening. The resin involved has a given index ofrefraction and a given density after curing.

The method then includes the steps of providing an opaque disc such asthe disc 18 of FIG. 1 of thermoplastic material having substantially thesame density as the above referred-to given density but constituting aplastic different from the polyester resin. The material of the disc hasthe characteristics of mechanically and chemically bonding with theresin without any surface deterioration. Further, this material has theproperty of swelling slightly on extended contact with the polyesterresin.

A holder corresponding to the annular ring 20 described in FIG. 1 isthen provided and constitutes a thermoplastic material which willmechanically and chemically bond with the polyester resin. Thethermoplastic material of the ring has the same index of refraction,transparency, Rockwell hardness and surface finishing characteristics asthe polyester resin.

In order to provide the symbol or numeral designation on the oppositefaces of the disc, there is provided an ink constituting a polyester andthermoplastic alloy which further functions as a catalyst for thepolyester resin and will bond to both the disc and the resin. This inkis silk-screened on each of the opposite faces of the disc by anappropriate mask defining the numeral 12 in the particular example setforth.

The disc is positioned in central coplanar relationship in the ring withthe ring lugs described in FIG. 1 engaging the periphery of the disc atequal circumferentially spaced points to hold it centered and provide adisc-ring assembly.

This disc-ring assembly is then positioned in the spherical cavity ofthe mold so that the center of the disc coincides with the center of thespherical cavity.

Next, the polyester resin is poured into the fill opening 28 tocompletely fill the cavity and thereby encapsulate this disc-ringassembly. Care must be taken to pour the resin in carefully and slowlyto avoid any possible entrapment of air bubbles. Essentially, however,there is only necessary a single pouring operation.

After the resin has cured with the disc-ring assembly encapsulatedtherein, the ring is substantially invisible. The cured sphere can thenbe removed from the mold by separating the mold halves in the event amold of the type described in FIG. 1 is employed.

Final steps of the method involve polishing the surface of the resultingsphere to provide the completed transparent polymer sphere.

It will be recalled that a characteristic of the thermoplastic materialcomprising the disc is that it swells slightly upon extended contactwith the polyester resin. Bonding of the disc and ink to each other andto the polyester resin thus results in an embossed characteristic forthe symbols, the uncovered surface portions of the disc swellingslightly. The further bonding of the ring with the disc and resinresults in a final sphere in which shock impacts are absorbed by thedisc, ink and ring as well as the resin as though the entire sphere werehomogeneous throughout.

The foregoing bonding characteristics of all of the components making upthe finalized pool ball minimize any risk of shattering of the ball uponimpact because of the uniform absorption of shock by the bondedconstituents. In other words, there are no "cleavage planes" which couldcause such shattering. Moreover, the bonding of the disc with thepolyester resin is effected without any surface deterioration and aminimization of any visible imperfections.

FIG. 5 illustrates the final product composition which, in theparticular embodiment described, constitutes a pool ball identified bythe numeral 12. While the actual diameter of the disc 18 is less thanthe outside diameter of the completed sphere, the disc will neverthelessappear to be of the same diameter because of the optical magnificationaccorded by the hemispherical clear resin portions on opposite sides ofthe disc.

The resulting transparent pool ball has many advantages in actual play.The rotational axis, for example, can immediately be identified byobserving the rotation of the disc when the ball is impelled by a cueball. This latter feature is important in controlling the amount of"English" applied to the ball.

The weight of the ball illustrated in FIG. 5 is 117 grams plus or minusthree grams. This weight or mass is less than that of a conventionalpool ball but results in a more "lively" action of the ball; forexample, better rebound and less moment of inertia. The diameter of theball corresponds to conventional pool balls and is equal to 57millimeters plus or minus 1 millimeter.

From all of the foregoing, it will be appreciated that the presentinvention provides a greatly improved shock resistant transparentpolymer sphere molding apparatus, method and product compositionparticularly useful in the provision of pool balls.

We claim:
 1. A method of manufacturing a shock resistant transparentpolymer sphere with a disc, having a symbol inked on each of itsopposite faces, diametrically incorporated in the sphere with the centerof gravity of the disc coincident with the center of gravity of thesphere, including the steps of:(a) providing a mold defining a sphericalcavity with a single fill opening at its top; (b) providing a giventransparent polyester resin in liquid form preparatory to pouring intosaid mold, said resin having a given index of refraction and a givendensity after curing; (c) providing an opaque disc of thermoplasticmaterial having substantially the same density as said given density butconstituting a plastic different from said polyester resin, saidmaterial having the characteristics of mechanically and chemicallybonding with said resin without any surface deterioration and whichmaterial swells slightly upon extended contact with said polyesterresin; (d) providing an ink constituting a polyester and thermoplasticalloy which will function as a catalyst for said thermoplastic resin andwill bind to both said disc and said resin; (e) providing a holder inthe form of an annular ring having a plurality of equallycircumferentially spaced lugs extending radially inwardly equaldistances, said ring being of thermoplastic material which willmechanically and chemically bond with said polyester resin, and whichhas the same index of refraction, transparency, Rockwell hardness andsurface finishing characteristics as said polyester resin after curing;(f) silk-screening said symbol on each of the opposite sides of saiddisc with said ink; (g) positioning said disc in central coplanarrelationship in said ring, said lugs engaging the periphery of said discat equal circumferentially spaced points to hold it centered to providea disc-ring assembly; (h) positioning said disc-ring assembly in saidspherical cavity of said mold so that the center of said disc coincideswith the center of said spherical cavity; (i) pouring said resin intosaid fill opening to completely fill said cavity and thereby encapsulatesaid disc-ring assembly; (j) removing the polyester resin with saiddisc-ring assembly encapsulated therein after curing, said ring beingsubstantially invisible; and (k) polishing the surface of the resultingsphere to provide said shock resistant transparent polymer sphere, thebonding of the disc and ink to each other and to the polyester resinresulting in an embossed characteristic for the symbols as a result ofsaid slight swelling of the disc material and the further bonding of thering with the disc and resin resulting in a sphere in which shock isabsorbed by the disc, ink and ring as well as the resin as though theentire sphere were homogeneous throughout.
 2. A method of manufacturinga shock resistant transparent polymer sphere with a disc, having asymbol on each of its opposite faces, diametrically incorporated in thesphere with the center of gravity of the disc coincident with the centerof gravity of the sphere, including the steps of:(a) providing a molddefining a spherical cavity with a single fill opening at its top; (b)providing a given transparent polyester resin in liquid form preparatoryto pouring into said mold, said resin having a given index of refractionand a given density after curing; (c) providing an opaque disc ofthermoplastic material having substantially the same density as saidgiven density but constituting a plastic different from said polyesterresin, said material having the characteristics of mechanically andchemically bonding with said resin without any surface deterioration andwhich material swells slightly upon extended contact with said polyesterresin; (d) providing a holder in the form of an annular ring having aplurality of equally circumferentially spaced lugs extending radiallyinwardly equal distances, said ring being of thermoplastic materialwhich will mechanically and chemically bond with said polyester resin,and which has the same index of refraction, transparency, Rockwellhardness, specific gravity and surface finishing characteristics as saidpolyester resin after curing; (e) providing said symbol on each of theopposite sides of said disc; (f) positioning said disc in centralcoplanar relationship in said ring, said lugs engaging the periphery ofsaid disc at equal circumferentially spaced points to hold it centeredto provide a disc-ring assembly; (g) positioning said disc-ring assemblyin said spherical cavity of said mold so that the center of said disccoincides with the center of said spherical cavity; (h) pouring saidresin into said fill opening to completely fill said cavity and therebyencapsulate said disc-ring assembly; (i) removing the polyester resinwith said disc-ring assembly encapsulated therein after curing, saidring being substantially invisible; and (j) polishing the surface of theresulting sphere to provide said shock resistant transparent polymersphere, the bonding of the disc to the polyester resin resulting in anembossed characteristic for the symbols as a result of said slightswelling of the disc material and the further bonding of the ring withthe disc and resin resulting in a sphere in which shock is absorbed bythe disc and ring as well as the resin as though the entire sphere werehomogenous throughout.